Ban assault weapons
As the population increases, the number of people who are so enraged as to take a gun and go out and kill people increases. Regardless of the reasons they have — hatred of others, self or mental instability — they are influenced by what they see and hear to take such action. Social media carries information on shootings, as does the media. This is not a criticism of the media or social media, simply the fact of the matter. More people with such a horrific bent get exposed and there are more copy-cat acts committed. So how to stop it?
You cannot stop it completely because someone will always find a way to get around laws or weapons of choice. The Oklahoma bomber used a fertilizer-based bomb to do his killing. What you can do about it is to limit their ability to get their hands on weapons and devices that make it easier to kill large numbers of people. Banning tactically configured, semi-automatic rifles derived from military rifle designs would be a small price to pay in trying to limit the carnage. Since these weapons are predominantly the choice of weapon for people committing these acts of violence, it would make sense to keep them out of their hands. If they were illegal to purchase and possess, one avenue to possession by would-be killers is closed off.
One may argue that such a move violates the constitutional 2nd Amendment, of course. However, on the other side of that argument is the basis on which the Constitution was written in the first place — right to life, liberty and the pursuit of happiness. Right to life is the very first priority and should supersede aspects of the 2nd Amendment that would prevent the banning of the so-called assault rifle. Society does not need assault rifles. And someone’s hobby or recreational pursuit being limited by a ban is not a very valid reason to allow these weapons to those who seek to kill as many people as possible.